Gaseous controlled fluidic throttling valve

ABSTRACT

A fluidic throttling valve for controlling flow in a pipe or conduit of a high density fluid, such as a liquid, by injecting a lower density fluid, such as an inert gas, into the pipe. In the preferred embodiment shown herein, this control gas is injected into a pipeline leading to a combustion engine to control the quantity of liquid flowing through that pipeline. The control gas is injected through a slot extending completely around the circumference of the pipe. The gas is injected at the throat section of a venturi constructed in the pipe to define a point of minimal cross-sectional area.

iJnited States Patent Rivard [451 May an, 1972 [54] GASEOUS CONTROLLEDFLUIDIC TEWOTTLING VALVE [72] Inventor: Jerome G. Rivard, Birmingham,Mich.

[73] Assignee: The Bendix Corporation [22] Filed: June 27, 1969 [21]App1.No.: 837,217

[52] US. Cl ..137/81-5, 137/251, 261/76, 138/45, 123/120 [51] Int. Cl...FlSc l/00 [58] FieldofSearch ...137/81 5,12, 14,251; 251/118, 124;261/75, 76, 78; 239/543, 544, 434.5; 60/243, 39.28; 73/207; 138/45;123/120 L4 if 14 Primary Examiner-William R. Cline Att0mey--William F.Thornton and Plante, Hartz, Smith & Thompson ABSTRACT A fluidicthrottling valve for controlling flow in a pipe or conduit of a highdensity fluid, such as a liquid, by injecting a lower density fluid,such as an inert gas, into the pipe. 1n the preferred embodiment shownherein, this control gas is injected into a pipelineleading to acombustion engine to control the quantity of liquid flowing through thatpipeline. The control gas is injected through a slot extendingcompletely around the circumference of the pipe. The gas is injected atthe throat section of a venturi constructed in the pipe to define apoint of minimal cross-sectional area.

11 Claims, 5 Drawing Figures Patented May 30, 19-72 3, 5,94

3 Shoots-Shut F5 JIWM/ jourae GASEOUS CONTROLLED FLUIDIC THROTTLINGVALVE BACKGROUND OF THE INVENTION 1. Field of the Invention Throttlingvalve for regulating the mass of fluid flowing in a conduit.

2. Description of the Prior Art It is well known by those skilled in theart that the quantity of a liquid flowing in a conduit or pipeline canbe altered by injecting a gas into that conduit. One device designed forregulating flow in this manner consists of a small gas injector pipedisposed within a larger liquid flow conduit. A control gas is injectedinto the flow conduit through a hole or holes in the injector pipe. Asthe gas enters the flow conduit, it displaces the flowing liquid.Therefore, as more gas is injected into the conduit, less liquid willflow. Since the injected gas has a molecular weight much lighter thanthe flowing liquid, the total mass of fluid flowing in a conduit can beconsiderably altered by this device. However, this device possesses anumber of faults that the valve of this invention overcomes. Forinstance, it takes a substantial quantity of gas to control liquid flowwith the above described device. In addition, the injector pipe disposedwithin the flow conduit creates a flow disturbance and resulting energylosses which make it difiicult to precisely control flow pressuredownstream from the valve. Further, an even mixing of the control gasand liquid is not achieved with the above described device which limitsits usefulness for situations in which it is desired to reduce but notcompletely stop the liquid flow.

It is also well known that a venturi can be constructed in a flow lineand used to define a point of minimal cross-sectional area for that flowline. The static pressure of the flowing liquid will be at a minimum atthis point of minimal cross-sectional area. A fluid injected into theflow line at this point will therefore meet with less resistance fromthe fluid flowing along the line than would be the case if that fluidwere injected at some other point. A number of devices make use of thesewell known principles. One such device augments the mass of fluidflowing to a rocket engine by injecting a liquid into a gas flow line atthe throat of a venturi when it is desired to increase the mass of fluidflowing to the rocket engine. Most carburetors also inject liquid fuelinto the gaseous air flow line at the throat of a venturi.

However, the above described venturi-injection devices differ from thedevice of this invention in that they inject high density fluid into aflow line carrying a fluid of lower density for the purpose ofincreasing the mass of fluid flowing per unit of time. They do not limitor restrict the flow of a high density fluid such as a liquid with amuch less dense fluid such as a gas as does the valve of this invention.

SUMMARY OF THE INVENTION This invention comprises an extremely efficientfluidic valve in which a small mass flow of low density fluid can beused to regulate the flow of large quantities of high density fluid. Inthe embodiments described herein, a gas is chosen to represent a lowdensity fluid, while a liquid represents a high density fluid. The valveherein described can be used to both reduce or throttle, and tocompletely shut off a flowing liquid. The valve of this inventionincludes means for injecting a control gas into a conduit or pipe froman aperture in its wall. An even mixing of the control gas and flowingliquid is provided by one embodiment of the invention in which controlgas is injected at a number of points around the periphery of a pipe,because the control gas will not have to penetrate as far to reach allportions of the flowing liquid as it would have to if it were injectedonly at a single point. In the preferred embodiments described herein,gas is injected into a pipe from a slot which extends around thecircumference of that pipe. The control gas is also injected in thepreferred embodiments shown herein at the throat of a venturi formed inthe pipe. The term venturi" is used herein as it is customarily used bythose skilled in this art and defines any tube or conduit having aconverging section, a throat section, and a diverging section. Theconverging section is designed to increase the velocity of the fluidflowing in the conduit and therefore lower the static pressure of thatfluid with a minimum energy loss. The diverging or diffuser section isconstructed to gradually increase the crosssectional area of the conduitto keep energy losses as low as possible and to efiectively convert theincrease in fluid velocity provided by the converging and throatsections of the venturi back to static pressure.

The valve illustrated herein includes a number of unique design featureswhich provide distinct advantages over other throttling valves. First,the venturi throat which defines the minimum cross-sectional area ofthis valve is designed to be as small as possible so that the quantityof control gas needed to regulate liquid flow will be minimized. Thatis, when a control gas is injected at a venturi throat where thecross-sectional flow area is minimized, the quantity of gas required todisplace a given quantity of liquid flow is less than that which wouldbe required if the gas were injected into the flow conduit at anotherpoint having a larger cross-sectional area. Thus a smaller volume of gascan be used to regulate flow than is possible with other devices. Theminimum cross-sectional area established by the venturi throat sectionalso provides a second advantage in that it aids mixing of the controlgas and the flowing liquid. Mixing is aided because the control gas neednot travel so far to completely penetrate and mix with the flowingliquid. And finally, since the liquid will be flowing fastest at thispoint of minimal cross-sectional area, its static pressure will be at aminimum. This static pressure is the pressure opposing perpendicularentry of the control gas into the flow conduit. Thus, control gas can beinjected into the venturi throat section at extremely low pressures toinitiate throttling. As throttling is increased, the static pressure inthe throat section also increases and reaches a maximum value when thecontrol gas is injected into the valve at a sufficient rate to shut offthe flowing liquid. However, the pressures needed to inject the controlgas into the venturi throat section of this valve to provide aparticular amount of throttling or to completely shut off the flowingliquid are small in comparison to the pressures needed by other fluidicvalves. The flowing liquid can be completely shut off with this valve byinjecting control gas at a pressure only slightly above the supplypressure of the flowing liquid.

Since the small venturi throat cross-section minimizes problems such aspenetration of the flowing liquid by the control gas, in one embodimentthe control gas is injected at an angle to the flowing liquid. Thecontrol gas thus acts to reduce the quantity of flowing liquid by bothdisplacing the liquid from at least portions of the flow line and byblocking or opposing the momentum of the flowing liquid.

One embodiment shown herein illustrates the valve of this invention in aliquid flow line leading to a rocket engine; another embodimentillustrates the valve of this invention placed in a fuel line leading toan automobile combustion engine. The valve of this invention, which isdefined by the appended claims, can certainly be included in a greatnumber of other devices. It is believed however, that both theadvantages and operating principles of this valve are particularly wellillustrated when shown of unique advantages over other valves used tosupply propellants to rocket engines and fuel to automobile engines. Forexample, propellant should be injected into a rocket engine at a fairlyconstant velocity regardless of the quantity of propellant flowing intothat engine per unit of time. This constant velocity injection isnecessary to assure even mixing of the two propellants, fuel andoxidizer, so that the engine will run smoothly. The valve of thisinvention provides a constant velocity output flow which issubstantially independent of the amount of throttling being provided bythe vvalves. The velocity of the flowing liquid will not significantlydecrease when the control gas is injected into the line, because theinjection of the control gas changes only the mass of fluid flowing fromthe valve and not the volume. It is also important that the control gasbe completely mixed with the liquid propellants when that gas is beingused to throttle rather than stop the rocket engine. Uneven mixing isprovided between the control gas and flowing liquid with this valvebecause the liquid static pressure which acts to oppose this mixing isminimized, and because the control gas need not penetrate very farbefore it will have reached all portions of the flowing liquid. Theinclusion of this valve in a fuel line leading to an automobile engineprovides a unique advantage in that the quantity of liquid fuel flowingto that engine can be varied without varying either the velocity atwhich the fuel flows to that engine or the length of the time intervalduring each engine cycle in which fuel flows to the engine. This is ofparticular advantage for automobile engines because the time intervalduring which an automobile engine is adapted to receive fuel is lowestwhen the engine is running at high speeds or in other words when itneeds the most fuel.

BRIEF DESCRIPTION OF THE DRAWINGS Further objects, features andadvantages of this invention will become apparent from a considerationof the following description, the appended claims, and the accompanyingdrawings in which:

FIG. 1 is a perspective view, partly in cross-section, of the injectionvalve of this invention shown in both the fuel and oxidizer lines to acombustor;

FIG. 2 is a perspective view of an embodiment of the injection valve ofthis invention in which the dimensions have been chosen so that vaporpockets form when liquid having a predetermined supply pressure passesthrough the valve;

FIG. 3 graphically illustrates the quantity of gas and injectionpressures needed to control liquid flow with a typical valve of thisinvention;

FIG. 4 is a perspective and cross-sectional view showing a modifiedembodiment of the valve of this invention;

FIG. 5 is a cross-sectional view of a portion of an automobilecombustion engine embodying one design of the gas injection valve ofthis invention in an engine fuel line.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to thedrawings, the rocket engine 10, illustrated in FIG. 1, includes twosimilarly designed fluidic valves 12 and 13, placed in a fuel pipeline14 and an oxidizer pipeline 16 respectively leading to a rocket enginecombustion chamber 18. A detailed description will be provided hereinfor the valve 12; it is understood that the construction, operation, anddesign consideration described below for the valve 12 also applies tothe valve 13. The valve 12 includes a venturi 20, having a convergingsection 21, a venturi throat section 22 and a venturi diffuser orrecovery section 24. The venturi throat section 22 establishes a pointof minimal cross-sectional area (A,) for the flow line 14. Injectionslot 26 extends completely around the inner circumference of the venturithroat at this point of minimal cross-sectional area. Thus, a solidsheet of control gas will be directed at the flowing liquid so thatthere will be a maximum mixing of the two fluids.

The minimum cross-sectional area A, of the venturi throat 22 is designedto be as small as possible and also maintain the static pressure of theflowing liquid in the venturi throat slightly above the vapor pressureof that liquid. The minimum cross-sectional throat area for the valve 12is determined by the maximum quantity of liquid it is desired to haveflow through the flow line 14. A pipeline may be reduced in size andstill pass a given quantity of liquid per unit of time if the liquidsupply pressure is increased. However, if this is done, the velocity ofthe flowing liquid at the reduced area will increase and its staticpressure will decrease. The minimum cross-sectional area of the venturithroat 22 is chosen so that when the maximum quantity of liquid neededby the rocket engine per unit of time flows through the line 14, thestatic pressure in the venturi throat 22 will be at or just above theFed/1. 'Jz p. (Pi-P.) where ab, the liquid weight rate of flow A,=venturi throat area p, liquid density P, liquid supply pressure Ccoefficient of discharge P, throat pressure g gravitational accelerationThe quantities 60,, p C P and 3 will be detennined in advance by thenature of the engine system 10 and rocket combustor 18. Ifthe system issuch that the liquid supply pressure can be varied, the maximum liquidsupply pressure would be substituted into the above equation. The valve12 is designed so that there will be no energy losses caused byvaporization of the flowing liquid in the valve 12. A pressure justslightly above the vapor pressure of the liquid would therefore besubstituted for P, in the above equation. Straightforward calculationproduces the value of the minimum venturi throat crosssectional area A,.Since both the flow cross-sectional area A, and the liquid staticpressure are minimized, a very small quantity of gas, which may beinjected at low pressures, will control the quantity of flowing liquid.

The diffuser or recovery portion 24 of the valve 12 has been chosen tohave a gradual cross-sectional area increase. This provides for a highpressure recovery downstream from the venturi valve. With the valveshown by the diagram of FIG. 1, the static pressure of the liquiddownstream from the venturi valve can be as high as nine-tenths of thestatic pressure of that liquid upstream from the valve. There will be nosignificant heat energy or pressure losses as the liquid fuel flowsthrough the valve 12. The venturi design provides a smooth, taperedchange in cross-sectional area so that energy will not be wasted in aturbulent flow resulting from an abrupt change in the cross-sectionalflow area in the pipe as is the case for other valves havingobstructions which are not shaped to form a venturi. Thus the pressure,and therefore the velocity, at which fuel enters the combustion chamber18 can be precisely and efficiently controlled upstream from the valve12.

In some situations however, it will be desirable to operate the valve112, as shown in FIG. 2, that is, as a cavitating venturi valve. As usedherein, the term cavitating venturi refers to any venturi in which thestatic pressure of the flowing fluid at some point is equal to the vaporpressure of that fluid so that a portion of the flowing liquidvaporizes. Vapor pockets 28 are shown in FIG. 2. A cavitating venturivalve differs from a noncavitating venturi valve in that there is alarger net liquid static pressure loss across the cavitating valve thanacross the noncavitating valve. That is, as has already been stated, thestatic pressure of the liquid downstream from the valve 12 illustratedin FIG. 1 can be as high as nine-tenths of the static pressure of theliquid upstream from that valve. In typical operation the maximum staticpressure for liquid downstream from the valve 112 illustrated in FIG. 2is about six-tenths of the static pressure of the liquid upstream fromthe valve 1 12. There are a number of ways of increasing the staticpressure drop across a venturi and thus providing a cavitating venturi.For instance, the valve 12 illustrated in FIG. 1 could be made tooperate as a cavitating venturi valve simply by reducing the load, orflow restriction, downstream from that valve. However, either thecombustion chamber 18 or the flow line leading to that chamber wouldhave to be changed in order to accomplish this change in downstream flowrestriction. The cavitation illustrated in FIG. 2 is provided by achange in the design of the valve 112 from that of the valve 12, and notby any change downstream from that valve. Valve 112 is similar to valve12 and includes a venturi having a converging section 121, a throatsection 122, and a diverging section 124.

Control gas is injected into the valve at the venturi throat section 122through an injection slot 126. Cavitation is provided because theminimum cross-sectional area A, of the venturi throat section 122 issmaller than the minimum cross-sectional area of the throat section 22of valve 12 and because the liquid supply pressure of liquid flowing tovalve 112 is higher than the liquid supply pressure of liquid flowing tovalve 12. The exact numerical value of the liquid supply pressurerequired to transmit any given weight rate of liquid flow (b, throughany given minimum throat cross-sectional area A, can be calculated fromequation (1). The numerical value of the minimum throat cross-sectionalarea A, is chosen in accordance with the amount of cavitation desired.

When a valve operates as shown in FIG. 2, it acts to isolate the flowrate from pressure fluctuations downstream from the venturi throat. Thatis, a pressure fluctuation downstream from the valve 112, due to say acombustion instability in the engine, will not affect the quantity ofliquid flowing from that cavitating venturi valve. An increase indownstream pressure merely acts to decrease the pressure differentialacross the valve 112, and therefore decreases the size of the vaporpockets 28. As the quantity of vapor in a venturi throat 122 decreases,the effective cross-sectional area of the venturi increases so that eventhough the pressure differential across the valve has been decreased,the quantity of liquid flowing from that valve will not change. Hence,the valve shown in FIG. 2 provides a constant quantity of liquid flow,not influenced by pressure fluctuations downstream from the valve.Because of this insensitivity to pressure fluctuations, the cavitatingventuri valve shown in FIG. 2 will be used in a number of instances eventhough a greater supply pressure P, must be used to maintain a givenliquid flow than is necessary to maintain the same flow rate through thevalve shown in the diagram of FIG. 1, and even though heat energy andtherefore pressure losses are introduced due to the vaporizing of theliquid in the venturi throat 122. With the valve 112 operating as shownin the diagram of FIG. 2, a combustion instability in an engine cannotstart a damaging dynamic pressure instability that could ultimatelycause the engine to explode as can be the case with other controlvalves. That is, one downstream pressure fluctuation will not influencethe quantity of liquid that will subsequently flow from the valve 112.With other valves, such a fluctuation'can produce an even greatersubsequent pressure fluctuation in the burning engine and start a chainreaction of increasing pressure fluctuations causing increasinglyviolent and uneven explosions in the engine.

FIG. 3 illustrates the operation of the valve of this invention andshows that a very small volume of gas, injected at moderately lowpressures into the flow line 14, will control liquid flow in that line.As discussed above, the venturi throat is chosen to establish a point ofminimal cross-sectional area A, for the flow line 14. Thus a minimumquantity of gas can be used to control liquid flow. Since A, isminimized, the liquid will flow with maximum velocity and have a minimumstatic pressure acting to oppose the injection of the control gas.Therefore, a minimum pressure is needed to inject the control gas intothe line 14 and mix two fluids which do not readily mix under ordinarycircumstances.

FIG. 3 graphically illustrates control of a liquid rocket fuel, 50percent UDMH and 50 percent hydrazine, flowing through the venturi valve12 having a minimum throat cross-sectional area of 0.000552 sq. in. Theliquid supply pressure is maintained at 200 lbs. per sq. in. Nitrogen,an inert gas, is used to control the liquid flow. It will be seen fromthis graph that 0.03 lbs. of liquid fuel flow through the completelyopened valve per second. As the control gas is injected into the throat22 of the venturi 12, it mixes with the flowing liquid and increases thethroat pressure P,. As more gas flows into the venturi throat section22, throat pressure P, increases so that it ultimately equals the liquidsupply pressure P,. At this point no liquid flows from the valve 12. Itwill be seen from the graph of FIG. 3 that a control gas supply pressureof 280 lbs, per sq. in. and a gas flow of only 0.003 lbs. per secondwill completely stop flow of the rocket fuel so that only the nitrogencontrol gas will flow from the valve 12.

The information supplied by the graph of FIG. 3 can be determinedexperimentally for a valve having any minimum cross-sectional flow area,injection slot area, liquid supply pressure, and control gas injectionpressure. The quantity of control gas and pressure at which that gasmust be injected in order to stop liquid flow from any valveconstruction can also be determined mathematically using thecompressible flow orifice equations which are well known to thoseskilled in the art.

FIG. 4 shows an alternate venturi valve design from that shown in FIGS.1 and 2. FIG. 4 illustrates a fluidic valve 30 in which a water dropletshaped obstruction 32 is held in the liquid flow line by thin air foilshaped members 34 to form the venturi portion of the flow line. The useof the water droplet shaped obstruction 32 is not a significant changefrom the design illustrated in FIGS. 1 and 2 and is merely shown toillustrate the second well known way of providing a venturi in a flowline. The valve 30 differs significantly from the valve 12, however, inthat the control gas is injected at an angle to the main flow linerather than perpendicular to that flow line. A control gas is injectedinto the flow line 14 at the venturi throat through an injection slot36. The injection slot 36 is constructed at an opposing angle to theflow line 14 so that the momentum of the incoming control gas acts notonly to cause that gas to penetrate the flowing liquid, but also acts toblock the flowing liquid. When the control gas is injected perpendicularto the liquid flow, its entire momentum acts to penetrate the flowingliquid. If the gas were injected in a direction exactly opposed to theliquid flow, the entire injection momentum would act to block or stopthe flowing liquid. When the angle of injection is chosen for maximumpenetration, there will be a minimal force acting to block the liquid,and conversely when the maximum blocking is obtained, penetration isminimized. Since it is desirable to have the control gas both block andpenetrate the flowing liquid, the valve design shown in FIG. 4, in whichthe control gas is injected with components of motion both perpendicularto and parallel to the flowing liquid, is an optimum one for manyapplications.

FIG. 5 shows the fluidic valve of this invention used to control thequantity of fuel flowing to a combustion chamber of a piston engine. Theengine 38 illustrated in FIG. 5 includes a cylinder of a typicalautomobile engine which includes a combustion chamber 40, piston 42,intake valve 44, exhaust valve 46, and spark plug 48. Since theconstruction and operation of piston engines is well known, theseelements will only be discussed herein to illustrate their relationshipto the operation of the fluidic valve 12 which is shown in FIG. 5 placedin a fuel flow line 50. The basic description of the valve 12 has alsoalready been provided above and will not be repeated here. The valve 12,which is controlled by the pulse control apparatus 52, regulates thequantity of fuel that will flow to the engine during successive enginecycles. The control apparatus 52 includes a variable flow signal logic54 which provides a control output signal in response to operatorcommands. This control output signal regulates a solenoid valve 56 andtherefore determines the quantity of control gas that will flow from asource of control gas 58 through a pipeline 60 to the valve 12. Theapparatus 52 is constructed so that the control signal from source 54regulates valve 56 mediately rather than immediately. The mediatecontrol of valve 56 is provided instead of attempting to operatedirectly with the output signal from the variable flow signal logic sothat the operation of valve 56 can be coordinated with piston positionof the operating engine. The control apparatus 52 therefore alsoincludes a signal source 62 which provides a cyclic signal determined byengine speed. That is, signal source 62 provides a higher frequencysignal when the engine 38 is running at a high rate of speed than whenit is running at a low rate of speed. This cyclic signal is transmittedto a signal shaping apparatus 64 where it is modified in accordance withthe nature of the control signal provided by source 54. This modified orshaped signal then operates the solenoid valve 56 directly.

The valve 12 and control apparatus 52 can operate in two different modesto control fuel flow through the line 50. That is, fuel flow can becontrolled either by varying the length of time during each engine cyclein which fuel is allowed to flow from the valve 12, or by varying thequantity of fuel allowed to flow during a particular fixed time intervalin successive engine cycles. This valve provides all of the previouslydescribed advantages, such as a constant velocity output flowsubstantially independent of the quantity of liquid flowing through thevalve in each of the above described modes of operation. However, eachmode of operation also provides several unique, additional advantageswhich are unique to that mode of operation.

Consider first the operation of the valve 12 when that valve isoperating to monitor fuel flow by controlling the length of time duringeach engine cycle in which fuel is allowed to flow to the engine. Inoperation, suppose a particular engine speed is being maintained and anoperator desires to increase that speed. To accomplish this speedincrease, he provides an input to the variable flow signal logic 54which produces a command signal for the signal shaping apparatus 64.This command signal modifies the signal shaping apparatus output signalso that the solenoid valve 56 will remain closed for a longer portion ofeach engine cycle. This decreases the time interval in each engine cycleduring which control gas will shut off the valve 12 and in turn allowsmore fuel to flow to the engine. Similarly, if the operator desires toslow the engine speed, he merely activates the variable flow signallogic 54 to provide a signal to the signal shaping apparatus 64 whichmodifies the output signal of that apparatus to open the solenoid valve56 for longer time intervals during each engine cycle. This increasesthe time during which control gas will shut off valve 12 and thereforereduces the time during which fuel is allowed to flow to the engine. Thetotal amount of fuel supplied to the engine and therefore the enginespeed is thereby reduced.

There are a number of advantages in constructing the control apparatus52 to operate the valve 12 to control fuel flow by varying only the timeintervals during which fuel is allowed to flow. One significantadvantage of the above described system lies in the fact that such asystem is relatively uncomplicated, inexpensive, and reliable. Thecontrol apparatus elements 54, 56, 62 and 64 are all simple, reliableand well known devices. The valve 56 is either opened completely toallow sufficient control gas to flow to the valve 12 to completely stopfuel flow, or the valve 56 is completely closed and allows no controlgas to flow to the valve 12 so that fuel flow is completelyunrestricted. No complicated apparatus is needed to provide anyintermediate quantity of control gas flow.

However, there are a number of disadvantages in varying the quantity offuel flowing to a piston engine by changing the length of a timeinterval during each engine cycle in which fuel is allowed to flow tothe engine. One disadvantage lies in the fact that the time intervalduring which fuel must flow to an engine to maintain a desired enginespeed is largest at high engine speeds when the intake portion of theengine cycle, that is the time during which valve 44 is opened, issmallest.

With the valve of this invention, the time interval during which fuelflows to the engine need not be changed in order to change the amount offuel flowing to the engine. The quantity of fuel flowing to an engineduring fuel intake can be varied by selecting a particular fixed timeinterval t, and varying the quantity of fuel allowed to flow to theengine during that time interval. Again, the solenoid valve 56 will becompletely opened and enough control gas will be injected into the valve12 at times other than during the intake time interval t of an enginecycle so that no fuel will flow from the valve 12 at those times. Enginespeed is controlled as follows. When it is desired to run the engines atmaximum speed, valve 56 is completely closed during the time interval1,, when fuel flows from the valve 12 to the combustion cylinder 40 sothat no control gas will be injected into the fuel flow line at thattime. When it is desired to run the engine at a slower speed, anoperator provides an input for the variable flow signal logic 54 of aform so that that logic provides an output signal which modifies theoutput signal from the signal shaper 64 to partially open valve 56.Thus, some control gas will be injected into the valve 12 during thetime interval t The quantity of control gas injected during this timeinterval is selected so that it will not stop the fuel flow as is thecase during other portions of an engine cycle, but is selected to reducethe quantity of fuel flowing to the engine. That is, when the engineruns at less than maximum speed, a mixture of fuel and control gas willflow from the valve 12 during the time interval 1,. At high enginespeeds the mixture will contain a relatively high portion of fuel andlow portion of control gas; at low engine speeds the relative quantitiesare changed so that more control gas and less fuel flows from the valve12.

This valve provides a number of advantages when operating to controlfuel flow by changing the quantity of fuel allowed to flow during aparticular fixed time interval instead of changing the length of thetime interval during which fuel is allowed to flow. First, fuel willflow from the valve 12 only during that portion of each engine cycleduring which valve 44 is open and the cylinder 40 is adapted to receivefuel. It will be unnecessary to have fuel flow from the valve 12 duringany other time interval even for extremely high engine speed. Second,this amplitude modulation, or in other words, the control of thequantity of fuel allowed to flow during a particular, fixed timeinterval, provides an extremely accurate control of the quantity of fuelallowed to flow to the engine. And finally, even though the quantity offuel allowed to flow during a particular time interval will be differentfor high and low engine speeds, the velocity at which that fuel flowsfrom the valve 12 will not change for high and low speeds. Thus, theengine system can be optimally designed to take advantage of aparticular, known flow velocity of the fuel from the valve 12 to thecombustion cylinders.

The fluidic valve 12 can be designed to possess a number of otheroperating characteristics which can be advantageous when the valve isplaced in environments such as shown in FIG. 5. For instance, the valve12 may be designed so that a fuel vapor rather than liquid fuel flowsfrom the valve venturi throat. The design considerations forconstruction of a valve to vaporize fuel flowing through it would be thesame as those discussed above with respect to FIGS. 1 and 2. If it isdesired to have a vaporized fuel flow supplied to the passageway 56, thevalve would be designed so that the static pressure of the flowing fuelin the venturi throat would be equal to the vapor pressure of theflowing fuel.

It will be noted with respect to FIG. 5 that the valve 12 is placedsubstantially at the end of the fuel flow line 50, and further that thediffuser portion 24 of that valve, that is the portion down-stream fromthe venturi throat, is chosen to be of a minimal length. This is done tomake the fuel supply system completely and quickly responsive to changesin the pressure of the control gas. When the pressure of the control gasis increased to stop fuel flowing through the valve 12 there will be avery short lag time during which fuel that had been downstream from thepoint at which the control gas is injected into the fuel flow linecontinues to flow toward the combustion chamber 40. The change inpressure of the control gas will very quickly change the composition ofthe fluid flowing into the combustion cylinder. Thus, a very sensitivecontrol is provided to exactly regulate the quantity of fuel flowing toan engine so that the proper amount of fuel flowsonly during the desiredportion of an engine cycle.

From the above description, it will be seen that this inventioncomprises a gas injection valve in which a control gas, preferably aninert gas, is injected into a fluid flow line at the throat of a venturiformed in that line. The cross-sectional flow area of the venturi valveis minimized at the point at which the control gas is injected. Thevalve of this invention possesses a number of advantages over othervalves. An extremely small quantity of a low density gas can be used toregulate and stop the flow of a high density liquid. When the valve isused to regulate rather than stop liquid flow completely, this valveprovides an even mixing between the control gas and the flowing liquid.This valve also maintains relatively constant flow velocity regardlessof the quantity of liquid flowing from this valve. These and otheradvantages make it particularly desirable to use this valve to controlthe liquid flow to a combustion engine. Of course, the numeratedadvantages will immediately suggest many other uses for this inventionto those skilled in the art. It will therefore be understood that boththe specific apparatus and application which are herein disclosed anddescribed are presented for purposes of explanation and illustration andare not intended to indicate limits of the invention, the scope of whichis defined by the following claims:

I claim:

I 1. A gas injection valve for controlling the quantity of liquidflowing in a conduit comprising:

a venturi in the conduit;

said venturi including a throat section having a preselected minimumcross sectional area for reducing the static pressure of the liquidflowing at a preselected rate to a preselected value; and

means for injecting a control gas having a lower density than thedensity of the liquid into the conduit at said venturi throat section tocontrol the quantity of liquid flowing in the conduit.

2. The valve set forth in claim 1 in which said minimum cross-sectionalarea is selected to reduce said static pressure for said liquid flowingat said preselected rate to a value just slightly above the vaporpressure of said flowing liquid at said point of minimum cross sectionalarea.

3. The valve set forth in claim 1 in which said cross-sectional area ofsaid throat section is chosen in accordance with the equation d A: 2g plt r)- where:

(i), the liquid weight rate of flow A, venturi throat area p liquiddensity P,-= liquid supply pressure C,, coefficient of discharge P,throat pressure g gravitational acceleration.

4. The valve set forth in claim 3 in which said minimum cross-sectionalarea is chosen so that the static pressure of said flowing liquid insaid venturi throat will approach but not reach the vapor pressure ofthat liquid when said liquid flows at said preselected rate.

5. The valve set forth in claim 1 in which said minimum cross-sectionalarea is chosen to cause a predetermined portion of said flowing liquidto vaporize when said liquid flows at a preselected rate.

6. The valve set forth in claim 1 in which said venturi includes athroat section and said injecting means includes a slot 0 extendingcompletely around the periphery of said venturi throat.

7. The valve set forth in claim 6 in which said injection slot isarranged at an opposing angle to the direction of liquid flow.

8. The valve set forth in claim 1 in which said control gas is an inertgas, and in which said injecting means is constructed to completely stopthe liquid flow.

9. In the fuel line to a piston engine a fuel control gas injectionvalve comprising:

a venturi formed in a section of the fuel line, said venturi including athroat section having a minimum cross-sectional area for reducing thestatic pressure of the fuel to a preselected value;

means for injecting a control gas into the fuel line at said venturithroat; and

means for controlling the rate of said injection of said control gas todetermine the quantity of said fuel flowing in said line. 10. Theinjection valve set forth in claim 9 in which said means for controllingthe rate of control gas injection is constructed to inject sufficientcontrol gas to stop fuel flow during preselected portions of successiveengine cycles, is constructed to allow fuel to How through said fuelline during other portions of successive engine cycles, and isconstructed to vary engine speeds by varying the pressure at which saidcontrol gas is injected into said fuel line during said other portions.

11. The injection valve set forth in claim 9 in which said means forcontrolling the rate of control gas injection is constructed to injectsufficient control gas into said fuel line to stop fuel flow duringpreselected portions of successive engine cycles, is constructed toallow fuel to flow through said fuel line during other portions ofsuccessive engine cycles, and is constructed to vary engine speeds byvarying the relative timelengths of said preselected and said otherportions of successive engine cycles.

1. A gas injection valve for controlling the quantity of liquid flowingin a conduit comprising: a venturi in the conduit; said venturiincluding a throat section having a preselected minimum cross sectionalarea for reducing the static pressure of the liquid flowing at apreselected rate to a preselected value; and means for injecting acontrol gas having a lower density than the density of the liquid intothe conduit at said venturi throat section to control the quantity ofliquid flowing in the conduit.
 2. The valve set forth in claim 1 inwhich said minimum cross-sectional area is selected to reduce saidstatic pressure for said liquid flowing at said preselected rate to avalue just slightly above the vapor pressure of said flowing liquid atsaid point of minimum cross sectional area.
 3. The valve set forth inclaim 1 in which said cross-sectional area of said throat section ischosen in accordance with the equation omega l Cd At Square Root 2g Rhol (Pl - Pt). where: omega l the liquid weight rate of flow At venturithroat area Rho l liquid density Pl liquid supply pressure Cdcoefficient of discharge Pt throat pressure g gravitationalacceleration.
 4. The valve set forth in claim 3 in which said minimumcross-sectional area is chosen so that the static pressure of saidflowing liquid in said venturi throat will approach but not reach thevapor pressure of that liquid when said liquid flows at said preselectedrate.
 5. The valve set forth in claim 1 in which said minimumcross-sectional area is chosen to cause a predetermined portion of saidflowing liquid to vaporize when said liquid flows at a preselected rate.6. The valve set forth in claim 1 in which said venturi includes athroat section and said injecting means includes a slot extendingcompletely around the periphery of said venturi throat.
 7. The valve setforth in claim 6 in which said injection slot is arranged at an opposingangle to the direction of liquid flow.
 8. The valve set forth in claim 1in which said control gas is an inert gas, and in which said injectingmeans is constructed to completely stop the liquid flow.
 9. In the fuelline to a piston engine a fuel control gas injection valve comprising: aventuri formed in a section of the fuel line, said venturi including athroat section having a minimum cross-sectional area for reducing thestatic pressure of the fuel to a preselected value; means for injectinga coNtrol gas into the fuel line at said venturi throat; and means forcontrolling the rate of said injection of said control gas to determinethe quantity of said fuel flowing in said line.
 10. The injection valveset forth in claim 9 in which said means for controlling the rate ofcontrol gas injection is constructed to inject sufficient control gas tostop fuel flow during preselected portions of successive engine cycles,is constructed to allow fuel to flow through said fuel line during otherportions of successive engine cycles, and is constructed to vary enginespeeds by varying the pressure at which said control gas is injectedinto said fuel line during said other portions.
 11. The injection valveset forth in claim 9 in which said means for controlling the rate ofcontrol gas injection is constructed to inject sufficient control gasinto said fuel line to stop fuel flow during preselected portions ofsuccessive engine cycles, is constructed to allow fuel to flow throughsaid fuel line during other portions of successive engine cycles, and isconstructed to vary engine speeds by varying the relative time-lengthsof said preselected and said other portions of successive engine cycles.